1. Field of the Invention
The present invention relates to methods for manufacturing liquid ejection heads, substrates for liquid ejection heads, and liquid ejection heads. Specifically, the present invention relates to methods for manufacturing ink-jet recording heads, which conduct recording by forming flying droplets by ejection of ink, by forming ink supply orifices for receiving ink into the ink-jet recording heads by anisotropic etching of silicon (Si), substrates for ink-jet recording heads, and ink-jet recording heads.
2. Description of the Related Art
Ink-jet recording apparatuses conducting recording by ejecting ink and adhering the ink to recording media are used in various types of office equipment such as printers, copiers, and facsimile machines. Generally, the ink-jet recording apparatuses each include an ink-jet recording head and an ink supply system for supplying ink to the head.
The ink-jet recording head is generally provided with ink ejection-energy-generating elements for generating energy for ejecting ink, ink ejection openings for ejecting ink, an ink channel communicating with each of the ink ejection openings, and an ink supply orifice for receiving ink from the ink supply system. Some of the ink-jet recording heads are a side-shooter type, i.e. ink droplets are ejected in the direction perpendicular to a substrate face on which the ink ejection-energy-generating elements are formed. In the side-shooter type ink-jet recording head, the ink supply orifice (liquid supply orifice) is generally formed as a through-hole in the substrate of silicon or the like (referred to as Si substrate, hereinafter).
The ink supply orifice of the through-hole can be formed by anisotropic etching of the Si substrate. Furthermore, U.S. Pat. No. 6,858,152 discloses a method for decreasing variation in formation width of the ink supply orifice caused by defects locally existing in the Si substrate. In the method, oxidation-induced stacking faults (OSFs) at an interface between the Si substrate to be etched and a SiO2 film used as a mask are formed. The density and thickness of the OSF regulate a side-etching rate, so that the effects of the defect in the substrate are decreased to reduce the variation in the formation width of the ink supply orifice; thus, yield ratios in manufacturing are improved.
In some ink-jet recording heads for color printing, a plurality of ink supply orifices are provided on a single silicon substrate in parallel to each other, and different inks are supplied from the respective ink supply orifices to eject inks of different colors. The ink-jet recording head having such a structure is required to minimize the substrate size of the recording head in order to achieve downsizing of the ink-jet recording head itself and to reduce a manufacturing cost of the ink-jet recording head. Therefore, a shorter distance between adjacent ink supply orifices is desirable.
However, it was found that the formation width of the ink supply orifices varies when the ink supply orifices are formed at an extremely short distance from each other by the method disclosed in U.S. Pat. No. 6,858,152. The present inventors have intensively studied and have found a new technological issue that just a little defect such as a pinhole in a masking material may affect the formation width of the ink supply orifices depending on the position of the defect.